Disk device with damper attached to arm of actuator assembly

ABSTRACT

According to one embodiment, a disk device includes a plurality of recording media each including a recording layer and an actuator assembly including an actuator block rotatably supported around a rotation shaft, a plurality of arms extending from the actuator block, and suspension assemblies respectively attached to the arms and supporting respective magnetic heads. Of the plurality of arms, at least one arm has vibration characteristics different from those of the other arms.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2020-155669, filed Sep. 16, 2020, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a disk drive.

BACKGROUND

As a disk drive, for example, a hard disk drive (HDD) comprises amagnetic disk installed in a housing, a spindle motor which supports anddrives to rotate the magnetic disk, a head actuator which supports themagnetic head, a voice coil motor which drives the head actuator and thelike. The head actuator comprises an actuator block including aplurality of arms and a suspension assembly, (which may be referred toas a head gimbal assembly (HGA)) attached to each arm to support themagnetic head.

Recently, as the storage capacity of the HDD increases, the number ofmagnetic disks installed is increasing accordingly. In order to dealwith a number of magnetic disks, the so-called split actuator has beenproposed, in which a head actuator is split into a plurality of, forexample, two head actuators each independently rotatable and the twohead actuators are disposed in a multilayered fashion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a hard disk drive (HDD)according to a first embodiment diagram, when a top cover is removed.

FIG. 2 is a perspective view showing an actuator assembly and a wiringsubstrate unit of the HDD.

FIG. 3 is a cross-sectional view of actuator assemblies which is in astate.

FIG. 4 is a cross-sectional view showing a part of the arm of theactuator assembly and a damper.

FIG. 5 is a cross-sectional view schematically showing an actuatorassembly of a HDD according to a second embodiment.

FIG. 6 is a plan view schematically showing arms of the actuatorassembly in the second embodiment.

FIG. 7 is a cross-sectional view schematically showing an actuatorassembly of a HDD according to a third embodiment.

FIG. 8 is a cross-sectional view schematically an actuator assembly of aHDD according to a fourth embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings.

In general, according to one embodiment, a disk device comprises aplurality of disk-shaped recording media each including a recordinglayer and an actuator assembly comprising an actuator block rotatablysupported around a rotation shaft, a plurality of arms extending fromthe actuator block, and suspension assemblies respectively attached tothe arms and supporting the respective magnetic heads. Of the pluralityof arms, at least one arm has vibration characteristics different fromthose of the other arms.

The disclosure is merely an example, and proper changes in keeping withthe spirit of the invention, which are easily conceivable by a person ofordinary skill in the art, come within the scope of the invention as amatter of course. In addition, in some cases, in order to make thedescription clearer, the widths, thicknesses, shapes and the like, ofthe respective parts are illustrated schematically in the drawings,rather than as an accurate representation of what is implemented.However, such schematic illustration is merely exemplary, and in no wayrestricts the interpretation of the invention. In addition, in thespecification and drawings, the same elements as those described inconnection with preceding drawings are denoted by like referencenumbers, and detailed description thereof is omitted unless necessary.

First Embodiment

As a disk drive, a hard disk drive (HDD) according to a first embodimentwill be described in detail.

FIG. 1 is an exploded perspective view of the HDD according to the firstembodiment, when a top cover thereof is removed. The HDD comprises aflat and substantially rectangular housing 10. The housing 10 includes arectangular box-shaped base 12 with an upper opening, and a top cover14. The base 12 includes a rectangular bottom wall 12 a opposing the topcover 14 with an interval therebetween, and side walls 12 b set to standalong circumferential edges of the bottom wall 12 a, which are formed tobe integrated as one body from, for example, aluminum. The top cover 14is formed into a rectangular plate shape of, for example, stainlesssteel. The top cover 14 is screwed to the side walls 12 b of the base 12by a plurality of screws 13 so as to close the upper opening of the base12.

In the housing 10 are provided a plurality of, for example, six magneticdisks 18 as recording media and a spindle motor 19 as a drive unit whichsupports and rotates the magnetic disks 18. The spindle motor 19 isdisposed on the bottom wall 12 a. Each magnetic disk 18 is formed tohave, for example, a diameter of 96 mm (approximately, 3.5 inches), andcomprises a magnetic recording layer(s) on upper and/or lower surfaces.The magnetic disks 18 are engaged with a hub (not shown) of the spindlemotor 19 so as to be coaxial with each other and are clamped by a clampspring 20 so as to be fixed to the hub. For example, the six magneticdisks 18 are placed parallel to each other in a multilayered manner withintervals therebetween. Further, the magnetic disks 18 are supported soas to be located parallel to the bottom wall 12 a of the base 12. Themagnetic disks 18 are rotated at a predetermined number of revolutionsby the spindle motor 19.

Note that the number of magnetic disks 18 is not limited to six, but itmay be increased or decreased.

The housing 10 includes therein a plurality of magnetic heads 17 whichperforms recording and reproduction of data with respective to themagnetic disks 18, respectively and a head actuator assembly, (which maybe referred to as a head actuator) which supports the magnetic heads 17movably with respect to the respective magnetic disks 18. In thisembodiment, the head actuator assembly is configured as split actuatorassembly divided into a plurality of actuator assemblies, that is, forexample, a first actuator assembly 22A and a second actuator assembly22B. The first and second actuator assemblies 22A and 22B are rotatablysupported around a common support shaft (a rotation shaft) 26 standingon the bottom wall 12 a of the base 12.

In the housing 10 are provided a voice coil motor (VCM) 24 which pivotsand positions the first and second actuator assemblies 22A and 22B, aramp load mechanism 25 which holds the magnetic heads 17 in an unloadposition spaced away from a respective magnetic disk 18 when themagnetic heads 17 move to an outermost circumference of the magneticdisk 18, and a wiring substrate unit (FPC unit) 21, on which electroniccomponents such as conversion connectors are mounted.

On an outer surface of the bottom wall 12 a, a printed circuit board(not shown) is fixed by screwing. The printed circuit board constitutesa controller, and the controller controls operation of the spindle motor19 and controls operation of the VCM 24 and the magnetic heads 17 viathe wiring substrate unit 21.

FIG. 2 is a perspective diagram showing the split actuator assembliesand the wiring substrate unit, and FIG. 3 is a cross-sectional view ofthe split actuator assemblies in order.

As shown in FIGS. 2 and 3, the split actuator assembly includes thefirst actuator assembly 22A and the second actuator assembly 22B. Thefirst and second actuator assemblies 22A and 22B are disposed in amultilayered manner one above another, and are provided to be rotatableindependently from each other around the common support shaft 26standing on the bottom wall 12 a of the base 12. The first actuatorassembly 22A and the second actuator assembly 22B are configured to havestructures substantially identical to each other. For example, the upperactuator assembly is referred to the first actuator assembly 22A, andthe lower actuator assembly is the second actuator assembly 22B.

The first actuator assembly 22A comprises an actuator block (a firstactuator block) 29, four arms 30 extending from the actuator block 29,head suspension assemblies, (which may be referred to as head gimbalassemblies (HGAs)) 32 respectively attached to the arms 30, and magneticheads 17 respectively supported by the head suspension assemblies. Theactuator block 29 comprises an inner hole 31, to which a bearing unit(unit bearing) 50 is mounted. The actuator block 29 is supportedrotatably on the support shaft 26 by the bearing unit 50.

In this embodiment, the actuator block 29 and the four arms 30 areformed to be integrated as one body from aluminum or the like, andconstitute a so-called E block. The arms 30 are each formed into, forexample, a slender flat plate shape, and extend from the actuator block29 in a direction normal to the support shaft 26. The four arms 30 areprovided parallel to each other with intervals respectively therebetweeneach other. In this embodiment, the four arms 30 are formed to havedimensions identical to each other and shapes identical to each other.

The first actuator assembly 22A includes a support frame 34 extendingfrom the actuator block 29 in a direction opposite to the arms 30. Avoice coil 36 is supported by the support frame 34. As shown in FIGS. 1and 2, the voice coil 36 is located between a pair of yokes 38 installedin the base 12 and it constitutes the VCM 24 together with the yokes 38and a magnet 39 secured to one of the yokes 38.

As shown in FIGS. 2 and 3, the first actuator assembly 22A comprises sixhead suspension assemblies 32, and the head suspension assemblies 32 arerespectively attached to extending ends of the respective arms 30. Thehead suspension assemblies 32 include up-head suspension assemblieswhich support the respective magnetic head 17 upward and down-headsuspension assemblies which support the respective magnetic head 17downward. The up-head and down-head suspension assemblies can be formedfrom head suspension assemblies of the same structure by placing them indifferent directions up and down. In this embodiment, in the firstactuator assembly 22A, a down-head suspension assembly is attached tothe uppermost arm 30, and an up-head suspension assembly is provided tothe lowermost arm 30 (30 a), and two head suspension assemblies of anup-head suspension assembly and a down-head suspension assembly areattached to each of the other two arms 30.

Six head suspension assemblies 32 extend from the four arms 30 and aredisposed substantially parallel to each other with regular intervalstherebetween respectively each other. Two magnetic heads 17 supported bya pair of a down-head suspension assembly 32 and an up-head suspensionassembly 32 are located to face each other with a predetermined intervaltherebetween. These magnetic heads 17 are located to oppose respectivesurfaces of the corresponding magnetic disk 18.

As illustrated schematically in FIG. 2, the suspension assemblies 32each comprise a slender plate spring-shaped suspension (a base plate anda load beam) and a slender belt-shaped flexure (a wiring member) 74. Adistal end-side portion of the flexure 74 is attached on surfaces of theload beam and the base plate, and a proximal end-side portion of theflexure 74 extend to a proximal end of the arm 30 along the arm 30. Themagnetic head 17 is mounted on a gimbal portion (an elastic supportportion) (not shown) provided at the distal end portion of the flexure74. Wiring lines of the flexure 74 are electrically connected to a readelement, a write element, a heater and other members of the magnetichead 17.

The proximal end-side portion of the flexure 74 is joined to aconnection portion (a wiring substrate) 46 of the flexibleprinted-circuit board (FPC), mounted on a mount surface of the actuatorblock 29.

The second actuator assembly 22B has a structure substantially identicalto that of the first actuator assembly 22A. That is, as shown in FIGS. 2and 3, the second actuator assembly 22B comprises an actuator block (asecond actuator block) 29 in which a bearing unit is built, four arms 30extending from the actuator block 29, six head suspension assemblies 32respectively attached to the arms 30, magnetic heads 17 mounted on therespective head suspension assemblies and a support frame 34 whichsupports the voice coil 36.

The actuator block 29 is supported rotatably by the support shaft 26 viathe bearing unit. The actuator block (the second actuator block) 29 issupported on a proximal end portion (a half portion on a bottom wall 12a side) of the support shaft 26, and is coaxially placed below the firstactuator block 29. The actuator block (the second actuator block) 29opposes the first actuator block 29 with a slight gap therebetween.

The actuator block 29 and the four arms 30 are formed to be integratedas one body from aluminum or the like, and constitutes the so-called Eblock. The arms 30 are each formed into, for example, a slender flatplate shape, and extend from the actuator block 29 in a direction normalto the support shaft 26. The four arms 30 are provided parallel to eachother with intervals respectively therebetween. In this embodiment, thefour arms 30 are formed to have dimensions identical to and shapesidentical to those of the arms 30 of the first actuator assembly 22A.

A lowermost arm 30 a of the first actuator assembly 22A and an uppermostarm 30 b of the second actuator assembly 22B are located most adjacentto a boundary between the first actuator assembly 22A and the secondactuator assembly 22B. The lowermost arm 30 a and the uppermost arm 30 bare disposed substantially parallel to each other with a predeterminedinterval therebetween.

The VCM 24 which drives the first actuator assembly 22A and the VCM 24which drives the second actuator assembly 22B are provided independentfrom each other. With this structure, the first actuator assembly 22Aand the second actuator assembly 22B can be driven (rotated) independentfrom each other around the support shaft 26.

As shown in FIGS. 2 and 3, in the first actuator assembly 22A and thesecond actuator assembly 22B, a damper 52 is attached to each arm 30. Inthe first actuator assembly 22A, dampers 52 are attached respectively toupper surfaces (upper surfaces facing a top cover 14 side) of theuppermost, second and third arms 30. A damper 52 a is attached on alower surface (a surface on a boundary side) of the lowermost arm 30 a.

In the second actuator assembly 22B, a damper 52 b is attached on anupper surface (a surface on a boundary side) of the uppermost arm 30 b,and dampers 52 are respectively attached on lower surfaces (lowersurfaces facing the bottom wall 12 a side) of the second, third andlowermost arms 30.

FIG. 4 is a cross-sectional view of an example of the damper.

As shown, each of the dampers 52, for example, the damper 52 b has adouble-layered structure of a viscoelastic layer V1 and a constraintlayer C1. The viscoelastic layer V1 is made of a viscoelastic material,and the constraint layer C1 is made of, for example, a material having arigidity higher than that of the viscoelastic layer, that is, stainlesssteel. The viscoelastic layer V1 and the constraint layer C1 are formedinto planar shapes substantially identical to each other and forexample, they are formed into planar shapes substantially the same asthe planar shape of the arms 30. The damper 52 covers the surface of therespective arm 30 while the viscoelastic layer V1 is attached on thesurface of the arm 30. When an arm 30 is deformed by vibration, theviscoelastic layer V1 between the arm 30 and the constraint layer C1 iswarped, thereby creating a vibration damping effect. Usually, as thethickness of the damper is greater or the plane area of the damper isgreater, the damping effect is enhanced.

As described above, in the actuator assemblies configured as describedabove, at least one arm 30 has vibration characteristics different fromthose of the other arms 30. According to this embodiment, as shown inFIG. 3, in the first actuator assembly 22A, the damper 52 a attached tothe lowermost arm 30 a (the arm most adjacent to the second actuatorassembly 22B) is formed thicker than the other dampers 52 respectivelyattached on the other arms 30. For example, when the thickness of theviscoelastic layer V1 of the dampers 52 is 50 μm and the thickness ofthe constraint layers C1 is 50 μm, the thickness of the viscoelasticlayer V1 of the damper 52 a is set to 80 to 100 μm, and the thickness ofconstraint layers C1 is 50 μm. Therefore, the damper 52 a can exhibits avibration damping effect higher than that of the other dampers 52. Thus,the lowermost arm 30 a on which the damper 52 a is attached, that is,the arm 30 a adjacent to the boundary between the actuator assemblies22A and 22B has vibration characteristics different from those of theother arms 30. Since the vibration damping effect is higher in thedamper 52 a than in the other dampers 52, and therefore the arm 30 a canreduce the generated vibration as compared to the other arms 30.

Note that in order to enhance the vibration damping characteristics ofthe damper 52 a, the constraint layer C1 thereof may be formed thickerthan the constraint layers of the other dampers 52 in place ofthickening the viscoelastic layer V1. Alternatively, both the thicknessof the viscoelastic layer V1 and the thickness of the constraint layerC1 of the damper 52 a may be set greater than the thickness of the otherdampers 52. Further, by using a material of the viscoelastic layer V1 orthe constraint layer C1 of the damper 52 a, different from that of thematerial of the damper 52, the vibration damping effect can be furtherenhanced.

In the second actuator assembly 22B, the damper 52 b attached to theuppermost arm 30 b (the arm most adjacent to the first actuator assembly22A) is formed thicker than the other dampers 52 respectively attachedonto the other arms 30. For example, when the thickness of theviscoelastic layer V1 of the dampers 52 is 50 μm and the thickness ofthe constraint layers C1 is 50 μm, the thickness of the viscoelasticlayer V1 of the damper 52 b is set to 80 to 100 μm, and the thickness ofconstraint layers C1 is 50 μm. Therefore, the damper 52 b can exhibits avibration damping effect higher than that of the other dampers 52. Thus,the uppermost arm 30 b on which the damper 52 b is attached, that is,the arm 30 b adjacent to the boundary between the actuator assemblies22A and 22B has vibration characteristics different from those of theother arms 30. Since the vibration damping effect is higher in thedamper 52 b than in the other dampers 52, and therefore the arm 30 b canreduce the generated vibration as compared to the other arms 30.

As shown in FIG. 2, the FPC unit 21 includes a first FPC unit 21 aconnected to the first actuator assembly 22A and a second FPC unit 21 bconnected to the second actuator assembly 22B.

The first FPC unit 21 a includes a substantially rectangular baseportion 42 a, a belt-like relay portion 44 a extending from one sideedge of the base portion 42 a, and a junction (a first wiring substrate)46 a continuously provided onto a distal end of the relay portion 44 a,which are integrated as one body. The base portion 42 a, the relayportion 44 a and the junction 46 a are formed from a flexibleprinted-circuit board (FPC). The flexible printed-circuit board includesan insulator layer such as of polyimide or the like, a conducting layerformed on the insulating layer, which forms wiring lines, contact padsand the like and a protective layer which covers the conducting layer.

On the base portion 42 a, electronic components including a conversionconnector 47 a and a plurality of capacitors (not shown) and the likeare mounted and are electrically connected to the wiring lines of theFPC. To the base portion 42 a, a metal band 45 a is attached, whichfunctions as a reinforcing plate. The metal band 45 a and the baseportion 42 a are each bent into substantially an L shape. The baseportion 42 a is disposed on the bottom wall 12 a of the base 12. Therelay portion 44 a extends from a side edge of the base portion 42 atowards the first actuator assembly 22A. The junction 46 a provided inthe extending end of the relay portion 44 a is attached onto one sidesurface (installation surface) of the first actuator block 29, andfurther fixed by screwing onto the installation surface by a fixingscrew.

A connecting end portion of each flexure 74 is disposed to overlay onthe junction 46 a and is electrically and mechanically joined to thejunction 46 a. Thus, the six magnetic heads 17 of the first actuatorassembly 22A are electrically connected to the base portion 42 a via thewiring lines of the flexure 74, the junction 46 a of the first FPC unit21 a and the relay portion 44 a, respectively. Further, the base portion42 a is electrically connected to the printed circuit board on a bottomsurface side of the housing 10 via the conversion connector 47 a.

Similarly, the second FPC unit 21 b includes a substantially rectangularbase portion 42 b, a belt-like relay portion 44 b extending from oneside edge of the base portion 42 b, and a junction (not shown)continuously provided onto a distal end of the relay portion 44 b, whichare integrated as one body. The base portion 42 b, the relay portion 44b and the junction are formed from a flexible printed-circuit board(FPC).

On the base portion 42 b, electronic components including the conversionconnector 47 b, capacitors (not shown) and the like are mounted and areelectrically connected to the wiring lines of the FPC. The base portion42 b is disposed to be adjacent to and in order with the base portion 42a of the first FPC unit 21 a and is installed on the bottom wall 12 a ofthe base 12. The relay portion 44 b extends from a side edge of the baseportion 42 b towards the second actuator assembly 22B. The junctionformed at the extending end of the relay portion 44 b is attached ontoone side surface (installation surface) of the second actuator block 29,and further fixed by screwing to the installation surface with fixingscrews.

The connecting end portion of each flexure 74 is disposed to be overlaidon the junction so as to be electrically and mechanically joined to thejunction. Thus, the six magnetic heads 17 of the second actuatorassembly 22B are electrically connected to the base portion 42 b via thewiring lines of the flexure 74, the junction of the second FPC unit 21 aand the relay portion 44 b, respectively. Furthermore, the base portion42 b is electrically connected to the printed circuit board on a bottomsurface side of the housing 10 via the conversion connector 47 b.

In the split actuator assembly configured as described above, thevibration of the first actuator assembly 22A and the vibration of thesecond actuator assembly 22B may interfere with each other via thesupport shaft 26. When such an interaction occurs, the vibrationalresponse in the vicinity of an axial central portion of the supportshaft 26 increases.

To avoid this, in the HDD of this embodiment, thick dampers 52 a and 52b are attached to the vicinity of the axial center of the support shaft26, more specifically, on the arm 30 a and the arm 30 b located near theboundary between the first actuator assembly 22A and the second actuatorassembly 22B. With this structure, if vibration occurs near the axialcentral portion of the support shaft 26, the vibration of the arms 30 aand 30 b can be effectively reduced. Thus, the contact between the arms30 a and 30 b and the respective magnetic disk 18 can be prevented,making it possible to improve the reliability.

Between the arm 30 a and arm 30 b, a magnetic disk 18 is not located,and therefore even if the thickness of the dampers 52 a and 52 b isincreased, the dampers do not approach a magnetic disk. With thisstructure, the contact between the dampers 52 a and 52 b and therespective magnetic disk 18 can be prevented, thereby making it possibleto improve the reliability.

As described above, according to the first embodiment, the vibration ofthe arms of the head actuators can be restrained, and thus a disk drivewith an improved reliability cab be obtained.

Next, HDDs according to other embodiments will be described. In theother embodiments to be described below, portions equivalent to those ofthe first embodiment are denoted by the same reference numbers anddetailed explanation is omitted or simplified, such explanation beingmainly given to portions different from those of the first embodiment.

Second Embodiment

FIG. 5 is a cross-sectional view schematically showing an actuatorassembly of an HDD according to a second embodiment, and FIG. 6 is aplan view schematically showing arms of the actuator assembly in thesecond embodiment.

As shown in FIG. 5, according to the second embodiment, dampers 52respectively attached to four arms 30 and 30 a of a first actuatorassembly 22A are all formed to have the same thickness. Dampers 52attached to four arms 30 and 30 b of a second actuator assembly 22B areall formed to have the same thickness.

In the actuator assembly, at least one arm 30 has vibrationcharacteristics different from those of the other arms 30. According tothis embodiment, in the first actuator assembly 22A, a lowermost arm 30a is formed into a shape different from that of the other three arms 30.FIG. 6, in part (a), shows a planar shape of the three arms 30 on anupper side. Each of these arms 30 is formed into a slender flat plateshape and comprises a plurality of through holes including a firstthrough hole 33. FIG. 6, in part (b), shows a planar shape of thelowermost arm 30 a. The arm 30 a is formed into a slender flat plateshape, and comprises a plurality of through holes including the firstthrough hole 33. Here, the first through hole 33 of the arm 30 a isgreater in open area than the first through holes 33 of the other arms30. That is, the arm 30 a has a plane area less than that of the otherarms 30, and a mass less than that of the other arms 30. Thus, thelowermost arm 30 a has vibration characteristics different from those ofthe other arms 30. The arm 30 a is formed to exhibit a characteristicfrequency different from that of the other arms 30.

In the second actuator assembly 22B, an uppermost arm 30 b is formedinto a shape different from that of the other three arms 30. FIG. 6, inpart (a), shows a planar shape of the three arms 30 on a lower side.Each of these arms 30 is formed into a slender flat plate shape andcomprises a plurality of through holes including a first through hole33. FIG. 6, in part (b), shows a planar shape of the uppermost arm 30 b.The arm 30 b is formed into a slender flat plate shape, and comprises aplurality of through holes including the first through hole 33. Here,the first through hole 33 of the arm 30 b is greater in open area thanthe first through holes 33 of the other arms 30. That is, the arm 30 bhas a plane area less than that of the other arms 30, and a mass lessthan that of the other arms 30. Thus, the lowermost arm 30 b hasvibration characteristics different from those of the other arms 30. Thearm 30 b is formed to exhibit a characteristic frequency different fromthat of the other arms 30.

In the second embodiment, the other configuration of the HDD is the sameas that of the HDD according to the first embodiment previouslydescribed.

According to the actuator assembly of the HDD configured as describedabove, if vibration occurs near the axial central portion of the supportshaft 26, the vibration can be attenuated by adjusting thecharacteristic frequency of each of the arms 30 a and 30 b located nearthe axial center of the support shaft 26, that is, near the boundarybetween the first actuator assembly 22A and the second actuator assembly22B. Thus, the contact between the arms 30 a and 30 b and the respectivemagnetic disk 18 can be prevented, making it possible to improve thereliability.

Note that the arms are not limited to the above-described configurationthat they are different in the shape and size of the first throughholes, but may be of such a configuration that the arms are different inouter shape and thickness.

Third Embodiment

FIG. 7 is a cross sectional view schematically showing an actuatorassembly of an HDD according to a third embodiment.

For increasing the vibration damping characteristics of a damper, theplane area of the damper can be set greater than that of the otherdampers in place of increasing the thickness of the damper. In the thirdembodiment, the dampers provided in at least one arm are formed to havea plane area greater than the plane areas of the dampers of the otherarms.

As shown in FIG. 7, the HDD of the third embodiment includes an oddnumber of, for example, five magnetic disks 18. The split actuatorassembly includes a first actuator assembly 22A and a second actuatorassembly 22B. The first and second actuator assemblies 22A and 22B aredisposed in a multilayered manner one above another, and are provided tobe rotatable independently from each other around the common supportshaft 26 standing on the bottom wall 12 a of the base 12. The firstactuator assembly 22A and the second actuator assembly 22B areconfigured to have structures substantially identical to each other.

The first actuator assembly 22A disposed on an upper side comprises anactuator block (a first actuator block) 29, three arms 30 extending fromthe actuator block 29, head suspension assemblies 32 respectivelyattached to the arms 30, and magnetic heads 17 respectively supported bythe head suspension assemblies.

The actuator block 29 and the three arms 30 are formed to be integratedas one body from aluminum or the like, and constitute the so-called Eblock. The arms 30 are each formed into, for example, a slender flatplate shape, and extend from the actuator block 29 along a directionnormal to the support shaft 26. The three arms 30 are provided parallelto each other with intervals respectively therebetween each other. Inthis embodiment, the three arms 30 are formed to have dimensionsidentical to each other and shapes identical to each other.

In this embodiment, in the first actuator assembly 22A, a down-headsuspension assembly is attached to the uppermost arm 30, and two headsuspension assemblies, namely, an up-head suspension assembly and adown-head suspension assembly are attached to each of the middle arms 30and the lowermost arm 30 a.

The second actuator assembly 22B disposed on a lower side comprises anactuator block (a second actuator block) 29, three arms 30 extendingfrom the actuator block 29, five head suspension assemblies 32respectively attached to the arms 30, magnetic heads 17 mounted on therespective head suspension assemblies and a support frame 34 whichsupports the voice coil.

The actuator block 29 is supported pivotably by the support shaft 26 viaa bearing unit. The actuator block (the second actuator block) 29 issupported by a proximal end portion (a half portion on a bottom wall 12a side) of the support shaft 26, and is coaxially placed below the firstactuator block 29. The actuator block (the second actuator block) 29opposes the first actuator block 29 with a slight gap therebetween.

The actuator block 29 and the three arms 30 are formed to be integratedas one body from aluminum or the like, and constitutes the so-called Eblock. The arms 30 are each formed into, for example, a slender flatplate shape, and extend from the actuator block 29 in a direction normalto the support shaft 26. The three arms 30 are provided parallel to eachother with intervals respectively therebetween. In this embodiment, thethree arms 30 are formed to have dimensions identical to and shapesidentical to those of the arms 30 of the first actuator assembly 22A.

A lowermost arm 30 a of the first actuator assembly 22A and an uppermostarm 30 b of the second actuator assembly 22B are located most adjacentto a boundary between the first actuator assembly 22A and the secondactuator assembly 22B. The lowermost arm 30 a and the uppermost arm 30 bare disposed substantially parallel to each other with a predeterminedinterval therebetween.

In this embodiment, in the second actuator assembly 22B, an up-headsuspension assembly is attached to the lowermost arm 30, and two headsuspension assemblies, namely, an up-head suspension assembly and adown-head suspension assembly are attached to each of the middle arms 30and the uppermost arm 30 b.

In the first actuator assembly 22A and the second actuator assembly 22B,ten head suspension assemblies 32 extend respectively from six arms 30and are placed substantially parallel to each other with predeterminedintervals respectively therebetween. Two magnetic heads 17 supported bya pair of a down-head suspension assembly 32 and an up-head suspensionassembly 32 are located to face each other with a predetermined intervaltherebetween. These magnetic heads 17 are located to oppose respectivesurfaces of the corresponding magnetic disk 18.

When there are an odd number of magnetic disks 18 are installed, themagnetic disk 18 located exactly in the middle along their stackingdirection is placed between the lowermost arm 30 a of the first actuatorassembly 22A and the uppermost arm 30 b of the second actuator assembly22B. Therefore, the magnetic head 17 of the down-head suspensionassembly 32 attached to the lowermost arm 30 a and the magnetic head 17of the up-head suspension assembly 32 attached to the uppermost arm 30 bare located to oppose respective surfaces of the central magnetic disk18.

The first actuator assembly 22A and the second actuator assembly 22B canbe independently driven (pivoted) around the support shaft 26.

In the first actuator assembly 22A and the second actuator assembly 22B,a damper 52 is attached to each arm 30. In the first actuator assembly22A, dampers 52 are attached respectively to upper surfaces (uppersurfaces facing a top cover 14 side) of two arms, that is, the uppermostand the middle arms 30. A damper 52 a is attached on a lower surface (asurface on a boundary side) of the lowermost arm 30 a.

In the second actuator assembly 22B, a damper 52 b is attached on anupper surface (a surface on a boundary side) of the uppermost arm 30 b,and dampers 52 are respectively attached on lower surfaces (lowersurfaces facing the bottom wall 12 a side) of two arms, the middle andthe lowermost arms 30.

In the actuator assemblies configured as above, at least one arm 30 hasvibration characteristics different from those of the other arms 30.According to this embodiment, in the first actuator assembly 22A, thedamper 52 a attached to the lowermost arm 30 a (the arm most adjacent tothe second actuator assembly 22B) is formed to have a plane area greaterthan the other dampers 52 respectively attached on the other arms 30.For example, the damper 52 a is formed to have a length along theextending direction of the arm 30, greater than the length of the otherdampers 52, and a plane area greater than that of the other dampers 52.Note that the dampers 52 and 52 a are set to have the same thickness.

The damper 52 a, with its larger plane area, can exhibit a vibrationdamping effect higher than that of the other dampers 52. Thus, thelowermost arm 30 a on which the damper 52 a is attached has vibrationcharacteristics different from those of the other arms 30. The damper 52a has a vibration damping effect higher than that of the other dampers52, and thus the arm 30 a exhibits can be effectively reduced ascompared to the other arms 30.

In the first actuator assembly 22A, the damper 52 b attached to theuppermost arm 30 b (the arm most adjacent to the first actuator assembly22A) is formed to have a plane area greater than the other dampers 52respectively attached on the other arms 30. For example, the damper 52 bis formed to have a length along the extending direction of the arm 30,greater than the length of the other dampers 52, and a plane areagreater than that of the other dampers 52. Note that the dampers 52 and52 b are set to have the same thickness.

The damper 52 a, with its larger plane area, can exhibit a vibrationdamping effect higher than that of the other dampers 52. Thus, theuppermost arm 30 b on which the damper 52 b is attached has vibrationcharacteristics different from those of the other arms 30. The damper 52b has a vibration damping effect higher than that of the other dampers52, and thus the arm 30 a exhibits can be effectively reduced ascompared to the other arms 30.

In the third embodiment, the other configurations of the actuatorassembly and the HDD are the same as those of the HDD according to thefirst embodiment previously described.

According to the actuator assembly of the HDD configured as describedabove, if vibration occurs near the axial central portion of the supportshaft 26, the vibration of each of the arms 30 a and 30 b located nearthe axial center of the support shaft 26, that is, near the boundarybetween the first actuator assembly 22A and the second actuator assembly22B can be attenuated. Thus, the contact between the arms 30 a and 30 band the respective magnetic disk 18 can be prevented, making it possibleto improve the reliability.

When there are an odd number of magnetic disks 18 are installed, themagnetic disk 18 located exactly in the middle is placed between the arm30 a and the arm 30 b. In this case, the dampers 52 a and 52 b attachedto the arms 30 a and 30 b approach close to the respective magnetic disk18, thus making it difficult to increase the thickness of the dampers 52a and 52 b. On the other hand, in this embodiment, the plane area of thedampers 52 a and 52 b can be set greater in place of increasing thethickness of the dampers. Thus, the vibration damping effect can beimproved while preventing contact between the dampers 52 a, 52 b and therespective magnetic disk 18.

As described above, according to the third embodiment, the vibration ofthe arms of the head actuators can be restrained, and thus a disk drivewith an improved reliability cab be obtained.

Fourth Embodiment

FIG. 8 is a cross-sectional view schematically showing an actuatorassembly of an HDD according to a fourth embodiment.

As shown, according to the fourth embodiment, an actuator assembly 22 ofthe HDD is configured as a single actuator assembly. The actuatorassembly 22 comprises an actuator block 29 rotatably supported by asupport shaft 26 via a bearing unit (not shown), seven arms 30 extendingfrom the actuator block 29, head suspension assemblies 32 attached tothe respective arms 30, and magnetic heads 17 supported by therespective head suspension assemblies.

The actuator block 29 and the seven arms 30 are formed to be integratedas one body from aluminum or the like, and constitute the so-called Eblock. The arms 30 are each formed into, for example, a slender flatplate shape, and extend from the actuator block 29 along a directionnormal to the support shaft 26. The seven arms 30 are provided parallelto each other with intervals respectively therebetween each other. Inthis embodiment, the seven arms 30 are formed to have dimensionsidentical to each other and shapes identical to each other.

The actuator assembly 22 comprises a support frame 34 extending from theactuator block 29 in a direction opposite to the arms 30. A voice coil(not shown) which constitutes the VCM is supported on the support frame34.

The actuator assembly 22 comprises twelve head suspension assemblies 32,and the head suspension assemblies 32 are attached respectively toextending ends of the arms 30. In the actuator assembly 22, a down-headsuspension assembly 32 is attached to an uppermost arm 30, and anup-head suspension assembly 32 is provided at a lowermost arm 30, andtwo head suspension assemblies, namely, the up-head suspension assembly32 and the down-head suspension assembly 32 are attached to each of theother five arms 30.

Two magnetic heads 17 supported by a pair of a down-head suspensionassembly 32 and an up-head suspension assembly 32 are located to faceeach other with a predetermined interval therebetween. The magneticheads 17 are located to oppose respective surface of the correspondingmagnetic disk 18.

In the actuator assembly 22 configured as described above, at least onearm 30 has vibration characteristics different from those of the otherarms 30. According to this embodiment, in the actuator assembly, adamper 52 is attached on an upper surface (a surface facing the topcover 14) of the uppermost arm, and a damper 52 is attached on a lowersurface (a surface facing the bottom wall 12 a side) of the lowermostarm 30.

As in the first embodiment described above, the dampers 52 have adouble-layered structure of a viscoelastic layer and a constraint layer.The viscoelastic layer is made of a viscoelastic material, and theconstraint layer is made of, for example, a material having a rigidityhigher than that of the viscoelastic layer, that is, stainless steel.The viscoelastic layer and the constraint layer are formed into planarshapes substantially identical to each other and for example, they areformed into planar shapes substantially the same as the planar shape ofthe arms 30. The damper 52 covers the surface of the respective arm 30while the viscoelastic layer is attached on the surface of the arm 30.When an arm 30 is deformed by vibration, the viscoelastic layer betweenthe arm 30 and the constraint layer is warped, thereby creating avibration damping effect.

As described above, the dampers 52 is attached respectively on theuppermost arm 30 and the lowermost arm 30, these arms have vibrationcharacteristics different from those of the other arms 30. That is, dueto the vibration damping effect of the dampers 52, the uppermost andlowermost arms 30 attenuate the vibration occurred, as compared to theother arms 30.

When an external impact or the like applied on the HDD, the vibration ofthe uppermost arm and the lowermost arm of the actuator assembly 22 canbe suppressed, thereby making it possible to prevent collision betweenthe respective arm 30 and the top cover 14, collision between therespective arm 30 and the bottom wall 12 a and contact between the arm30 and the magnetic disk 18. As described above, in the third embodimentas well, the vibration of the arm of the actuator assembly isrestrained, and thus a disk drive with improved reliability can beobtained.

Note that the structure in which the arms have different vibrationcharacteristics is not limited to the case where dampers are attached,but such a configuration will do that arms are formed to have a shapedifferent from the shape of the other arms.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The head actuator assembly can be divided into not only two, that is,the first and second actuator assemblies, but also three or more. Thenumber of magnetic disks is not limited to six, but it may be five orless, or seven or more. The number of arms, that of head suspensionassemblies, and the number of magnetic heads may be increased anddecreased according to the number of magnetic disks installed.

The arms of different vibration characteristics are not limited to theuppermost and lowermost arms, but any other arms can be selected. Thematerial, shape, size and the like of the elements which constitute thedisk drive are not limited those of the embodiments, but they may bechanged in various ways as needed.

What is claimed is:
 1. A disk device comprising: a plurality of disk-shaped recording media each comprising a recording layer; a first actuator assembly comprising a first actuator block rotatably supported around a rotation shaft, a plurality of first arms extending from the first actuator block, a plurality of first suspension assemblies respectively attached to the plurality of first arms and respectively supporting a plurality of first respective magnetic heads, and a plurality of first dampers respectively attached to at least two arms of the plurality of first arms; and a second actuator assembly comprising a second actuator block rotatably supported around the rotation shaft, the second actuator block opposing the first actuator block with an interval therebetween, a plurality of second arms extending from the second actuator block, and a plurality of second suspension assemblies respectively attached to the plurality of second arms and respectively supporting a plurality of second magnetic heads, wherein, for one arm of the plurality of first arms that is the closest to the second actuator assembly of all the first arms, a first damper is attached that is thicker than any of the first dampers respectively attached to other first arms.
 2. The device of claim 1, wherein the second actuator assembly further comprises a plurality of second dampers respectively attached to at least two arms of the plurality of second arms, and for one arm of the plurality of second arms that is the closest to the first actuator assembly of all the second arms, a second damper is attached that is thicker than any of the second dampers respectively attached to other second arms. 